399880009 has 3 divisors (see below), whose sum is σ = 399900007. Its totient is φ = 399860012.

The previous prime is 399880003. The next prime is 399880021. The reversal of 399880009 is 900088993.

The square root of 399880009 is 19997.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 900088993 = 3709 ⋅242677.

It can be written as a sum of positive squares in only one way, i.e., 347636025 + 52243984 = 18645^2 + 7228^2 .

It is a de Polignac number, because none of the positive numbers 2^k-399880009 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (399880003) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 9999 + ... + 29995.

Almost surely, 2^399880009 is an apocalyptic number.

399880009 is the 19997-th square number.

399880009 is the 9999-th centered octagonal number.

It is an amenable number.

399880009 is a deficient number, since it is larger than the sum of its proper divisors (19998).

399880009 is an frugal number, since it uses more digits than its factorization.

399880009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39994 (or 19997 counting only the distinct ones).

The product of its (nonzero) digits is 139968, while the sum is 46.

The cubic root of 399880009 is about 736.7326172560.

The spelling of 399880009 in words is "three hundred ninety-nine million, eight hundred eighty thousand, nine".